1. Field of the Invention
The invention pertains to the mounting of a fan blade assembly to a thermally controlled or externally controlled drive clutch wherein the fan blade assembly includes synthetic blades and a hub capable of being placed upon the clutch body cooling fins.
2. Description of the Related Art
Internal combustion engines, including diesel engines, regulate the engine coolant temperature by the use of fan blades drawing or pushing air through a heat conducting radiator. As the rotation of the fan assembly requires considerable energy, for some time it has been popular to mount the fan or blade assembly upon a thermally controlled clutch or drive mechanism powered from the engine. The thermal clutch utilizes temperature sensitive control means either sensing the temperature of the ambient air, or the engine temperature, wherein the clutch drives the fan only when forced ventilation through the coolant radiator is required, for instance, when the vehicle is at rest or moving at low speeds, or under heavy load such as when climbing an incline.
A thermally controlled fan clutch usually permits the fan to be in a non-driven mode during normal vehicle movement as air will pass through the coolant radiator due to the vehicle movement thereby conserving energy and improving fuel efficiency.
The use of thermally controlled clutches and fan drive couplings is well known and a typical device is shown in U.S. Pat. No. 3,262,528. It is also known to use blade assemblies wherein the blades are formed of a synthetic plastic material as employed in conjunction with a thermally controlled clutch or coupling as shown in U.S. Pat. Nos. 4,169,693, 4,238,016, 4,282,961 and 5,358,382. However, in the known prior art, the mounting of the blade assembly upon the clutch is usually by means of threaded fasteners requiring expensive drilling and threading of the various components, and "bolt-on" blade assemblies may easily be misassembled or misaligned during assembly and installation and are subject to unloosing due to vibration, and the bolts add an objectionable axial length to the assembly.